1. Field of the Invention
The present invention relates to an X-ray sensing method and apparatus with a photoelectric conversion element driving control, and a photoelectric conversion element. In particular, the present invention relates to an X-ray sensing method and apparatus, in which consideration is given to a photoelectric conversion element driving range and reading range, and a photoelectric conversion element.
2. Related Background Art
With a conventional X-ray sensing apparatus, an X-ray beam is projected from an X-ray source so as to pass through an analysis subject such as a medical patient, and the X-ray beam having passed through the subject is sensed by a screen film cassette, a film auto-changer, computed radiography (CR), a flat panel detector (FPD), or the like.
In the field of X-ray radiographs, a high-resolution solid-state X-ray detector using the FPD is proposed. This detector includes an X-ray sensor comprising a two-dimensional array of photoelectric conversion elements such as photodiodes typically, in which 3000 to 4000 photoelectric conversion elements are arranged in each dimension of the array. Each photoelectric conversion element generates an electric signal corresponding to the amount of X rays incident onto the X-ray sensor. With this construction, a subject is positioned between the X-ray source and the X-ray sensor, and the amount of X rays having passed through the subject is converted into electric signals, thereby obtaining an X-ray image of the subject. Also, the signal from each photoelectric conversion element is independently read, digitized, subjected to image processing, and stored and displayed. Such a detector is disclosed in Japanese Patent Application Laid-Open No. 09-257944, for instance.
Further, with the reduction in thickness and the improvement in high reliability techniques, the solid-state X-ray detector using the FPD is also on its way to size and thickness reduction, while the X-ray screen film cassette has attained such the reduction.
The solid-state X-ray detector using the FPD, however, suffers from a problem that a large amount of electric power is consumed to drive the photoelectric conversion elements of the X-ray sensor. In particular, when a battery is built into a thin and small-sized X-ray digital sensing apparatus, for instance, it is required to attain a driving in which the amount of electric power consumed by the X-ray sensing apparatus at the time of ordinary sensing can be reduced.